Fuselages and wings of aircraft may include support structures, such as stringers, to help the fuselage and wings maintain their shape under various stress and strain conditions. In some examples, each stringer may include a gap adjacent a skin of the fuselage or the wings. The gaps may be filled to provide strength and/or rigidity to the stringer assembly. The size, shape, and/or configuration of a stringer may impact one or more performance attribute(s) associated with the stringer. For example, the size, shape, and/or configuration of a stringer may impact a pull-off strength associated with the stringer when the stringer is coupled to a composite structure of an aircraft such as a skin of a fuselage or wing.